This disclosure relates to air inerting systems for aircraft, and more specifically to a method of inert gas management requiring dehumidification.
Aircraft fuel tanks can contain potentially combustible combinations of oxygen, fuel vapors, and ignition sources. In order to prevent combustion, the ullagez of fuel tanks and contained space is filled with inert air containing less than 12% oxygen. Conventional fuel tank inerting (FTI) methods include air separation module (ASM) methods that separate ambient air into nitrogen-enriched air, which is directed to fuel tanks and locations needing inerting, such as fire suppression systems, and oxygen-enriched air, which is rejected overboard. But ASM methods require pressurized air to produce dry oxygen-depleted air suitable for inerting.
As an alternative, proton exchange membrane (PEM) electrochemical gas separators can generate inert gas that is saturated with water vapor without bleeding an engine compressor stage. However, the water vapor must be removed if it is to be used for fuel tank inerting purposes, otherwise water in fuel tanks creates a plethora of problems, including degrading fuel quality, freezing and occluding fuel system passages, and feeding growth of microbes. Condensers are limited in their use for drying because the inert gas must be dried to a subfreezing equivalent dew point for condensers to remove enough water from inert air. Other previous methods use low pressure bleed air for hybrid PEM and ASM technology, but a solution to dry humid oxygen-depleted air produced in PEM devices that is independent of a pressurized supply of air is needed.